This invention relates to knee joints for anthropomorphic dummies used in crash testing of motor vehicles and is particularly an improvement of the knee joint shown in the U.S. patent application Ser. No. 061,018, filed by James O. Kortge on July 26, 1979 and assigned to the assignee of this application, and now U.S. Pat. No. 4,235,025.
Prior art anthropomorphic dummies used for vehicle crash testing generally had knee joints comprising simple hinges which allowed only rotation of the tibia with respect to the femur about the axis of the hinge. However, the actual knee of a human vehicle occupant in a seated position with the tibia at an approximate right angle to the femur may exhibit a translational or shearing motion between the tibia and femur when the knee or tibia is subjected to a frontal load of sufficient magnitude. Additionally, recent research has provided some indication of the allowable femur to tibia translational motion which the human knee can withstand before knee injury occurs. Therefore, it may be possible to test for shearing knee injuries in vehicle crash tests if a dummy knee is provided which allows such translational shearing motion when the tibia is in an approximate right angle to the femur. To prevent the recording of false data on such shearing motion, the knee design should not allow such shearing motion from a frontal load when the tibia is in line with the femur as when the lower leg is raised, since the allowable stress to the knee is different in that leg configuration.
The aforementioned Kortge patent application discloses a dummy knee joint which should provide the required rotational motion and translational motion of the tibia at a substantially right angle to its direction while preventing translational motion of the tibia parallel to its own direction. However, that design fails to provide some features which would be quite desirable in a practical working model of such a dummy knee joint. For example, it would be desirable to provide means for independently adjusting the rotational friction of the knee joint to simulate that of the human knee. In addition, it would be desirable for reproducible test results to define a specific zero or no load translational position of the tibia with respect to the femur, so that the reference readings of the motion transducers may be established. It would also be desirable to provide such a knee joint which is self-contained with few projecting parts which might be susceptible to breakage or misalignment and able to be fit within the present dummy leg without redesign of that leg.